Electrical cycling timer



June 8, 1965 A. w. sKooG ETAL ELECTRICAL CYCLING TIMER Filed NOV. 2. 1961 INVENTORS A. WARREN SKOOG FLORIAN E. TEPOLT (,d. EQ, ATToRN Y United lStates Patent 3,133,502 ELECTRlCAL CYCLING T/IER Arthur W. Sheng, Clinton, and Florian E. Tepoit, Utica, N.Y., assignors to The Bendix Corporation, Oneida, N.Y., a corporation of Delaware Filed Nov. 2, 1961, Ser. No. 149,615 6 Claims. (Cl. 307-132) This invention relates to electric timing apparatus and more particularly concerns a cycling timer having PN unijunction transistor control circuit.

An object of the present invention is to provide an improved timer in which an actuating coil is energized at predetermined intervals upon actuation of PN unijunction transistor.

A further object is to provide an electrical cycling apparatus in which capacitance means periodically trigger ya PN unijunction transistor so that an actuating coil is energized.

Another object is to provide such an electrical cycling apparatus in which resistance-capacitance means and the transistor cooperate with a control relay and stepper switch to provide operation at predetermined intervals.

An additional object is the provision of such apparatus in which the capacitance means is residually-discharged by operation of the stepper switch so that the control relay circuit is deenergized.

The realization of the above objects along with the features and advantages of the invention will be app-arent from the following description and the accompanying drawing.

The drawing is a diagrammatic showing of an electrical timer embodying the invention and shows a stepper switch which is rotated after a predetermined time delay resulting rom circuitry having a control relay, PN unijunction transistor, and delay means for triggering the transistor.

Referring to the drawing, the battery or other source of 28-volt direct current 11 has a positive terminal 13 and a negative terminal 15. Negative terminal is also represented by a ground symbol in the lower part of the drawing. The positive terminal 13 is connected to control switch 17 which connects through resistor 19 to the second base connector 21 ofthe PN unijunction transistor 23. Resistor 19 is a temperature compensating resistor which automatically compensates for changes in ambient temperature to give consistent timing. A irst circuit is thus provided from the battery 11 to transistor base 21. The other or iirst base connector 25 of the transistor 23 has a ground connection provided by a wire 27 connected vto ground or the negative terminal 15 of the battery 11.

A second circuit is provided from the control switch 17 by wire 31, timing resistor 33, wire 35, actuating or relay coil 37 and wire 39 to the emitter 41 of the transistor 23. This silicon transistor 23 has the characteristic that there is no current flow between its emitter and its first hase until the voltage therebetween is 0.56 of the voltage between the two bases or about 22 volts. When this triggering Voltage is reached, current hows between the emitter and the first base. Due to timing resistor 33, vthis triggering voltage is not reached solely via the second circuit from and to the battery 11.

Capacitance means in the form of two capacitors 42 and 43 in parallel is connected to the ground wire 27 oi transistor first base connector by wires 45 and 46 and is connected to the second circuit between the timing resistor 33 and the relay coil 37 by wire 47. This arrangement permits capacitors 42 and 43 to provide the triggering voltage for the transistor 23 since the capacitor voltage will be impressed from the emitter 41 to the first base 25. It is apparent that capacitors 42 and 43 are selected so that they build up the transistor triggering voltage and provide an rice energizing current through actuating or relay coil 37 in cooperation with timing resistor 33.

The relay coil 37 is part of relay 51 (indicated by the dashed line box) which includes two normally-open switches 52 and 53 in parallel.

Contacts 54 and 55 of both switches are connected to control switch 17 by wire 56. The movable elements 57 and 53 are connected to wire 59 which leads to the stepper switch solenoid or coil 61. Solenoid 61 is connected by wire 62 and wire 46 to the ground connection 27 so that, when relay 51 is operated, solenoid 61 is energized.

Solenoid 61 is part of a stepper switch 63 indicated by dashed lines and including rotating switch 65. Stepper switch 63 is shown diagrammatically and is similar to the switch shown in U.S. Patent No. 2,803,814. The solenoid-actuated movable switch element 67 of solenoid switch 63 is mechanically-linked (indicated bythe dashed line) to the rotary contact 71 so that it rotates to provide an electrical connection therefrom to the circularly-arranged contacts 72. Contacts 72 can be connected to solenoid valves which control the inliating of different deicing boot sections on an aircraft.

Stepper switch 63 has its movable switch element 67 connected into the second circuit between relay coil 37 and timing resistor 33 by wire 73 and has its solenoid switch contact 75 connected by wire 76 to the wire 62 providing a ground connection for solenoid 61. With this arrangement, capacitors 42 and 43 are provided with a discharge path when solenoid switch 68 is closed. lt is apparent that, when relay 51 is closed, stepper switch 63 will rotate rotary element 71 and will close its solenoid switch 68 so that capacitors 42 and 43 can discharge after having triggered transistor 23 and energize relay coil 37.

Relay 51 is provided with arc suppression means when being de-energized and the movable elements 57 and 58 move to open position. For this purpose, a capacitor 81 and a resistor S2 are connected in series across the movable elements and the normally-open contacts 54 and 55 by being connected to wires 56 and 59. Any charge from capacitor 81 derived from solenoid 61 is discharged by the low-value, bleed-oit resistor 83 connected from Contact 84 of relay switch 53 to wire 46 which is grounded.

In operation when it is desired to operate stepper switch 63 at predetermined intervals of time, control switch 17 is closed. This establishes a voltage across the two bases of the transistor 23 and initiates a build-up of charge in capacitors 42 and 43. Resistor 33 limits the voltage across the emitter 41 and iirst base 25 of the transistor 23 to a value much below the triggering voltage. `Resistor 33 governs the time required for capacitors 42 and 43 to become suii'iciently charged to trigger the transistor 23 and to actuate the relay coil 37. Coil 37 is actuated A when the current in the capacitors 42 and 43 builds up to the critical value.

Upon the triggering of transistor 23, the coil 37 is energized to its operating level so that parallel switches 52 and 53 of relay 51 are closed and current is supplied to solenoid 61 of the rotary stepping switch 63. Solenoid 61 when thus energized rotates through the mechanical linkage the rotary contact 71 one step to the next contact 72. The solenoid switch 68 closes so that the capacitors 42 and 43 are discharged through the grounding circuit including wires 35, 73, 76, 62 and 46. Upon discharge of the capacitors 42 and 43, the transistor 23 is tie-triggered with the result thatvrelay 51 is de-energized and opens which causes solenoid switch 68 to open. This resets the timing apparatus for operation so that the cycling is repeated automatically. Sparking across relay switches 52 and 53 when their contacts are opened and break the liow of current is minimized by capacitor 81 and resistor 82. The bleed-oil? resistor 83 quickly disaiaasoa charges the arc-suppression capacitor 81 to protect against metal transfer between the contacts when again closed. The resistor 19 in serieswith the transistor 23 maintains a consistent timing cycle by automatically compensating for changes in ambient temperature.

From-the foregoing, it can be realized that the switching of the transistor 23I is controlled: through its emitter circuit by resistor 33t and capacitors 42 and 43 and that the relaycoil 37 is actuated' when the current in the capacitors builds up to the critical value. The time required for the capacitors to become charged suiiiciently to trigger the transistor 23' and to actuate the relay- 51 is governedY by the value of the resistor 33. The control rrelay does not require a specific drop-out wattage because the relay coil is in the emitter circuitl of the' unijunction transistor. The transistor is shut ofi immediately when the solenoid switch shorts out the capacitors. Since, at thestart ofeach cycle, the capacitors are |discharged, a uniform time delay starting condition is provided; Thereafter, the capacitors function with the timingl resistor tov provide a predeterminedA timing interval and then toA actuate and hold the control relay for opera-tion ofthe stepperswitch. It is apparent that, for

` different timing, other resistors can be conveniently substituted for resistor 33.

In a cycling timer giving af time interval of ten vseconds, the characteristics ofthe componentswere as follows:

Transistor (23)- General Electric 2N489. Resistor (19) 1000 ohms.

Resistor (33)v 100,000 ohms. Capacitors (42, 43) 68mfd. (each).

Coil (37) 400 ohms.

Capacitor (81) .25 mvfd.

Resistor-(82) 47 ohms.

Solenoid (61) S'Ohms.

Resistor (83)- 39 ohms.

aground connection; a second circuit connecting saidr control switehthrough a timing resistor and an actuator coil to said emitter, capacitance means connected to said tirst base connector and to said second circuit at a point between said actuator coil and said timing resistor, said transistor being triggered when said capacitance means is charged to a predetermined value so. that said actuator Y coil is energized, means operable bysaid'actuator coil when energized to provide after a' predetermined iixed time delay a temporaryY discharge path for said' capacitance means and then to opensaid discharge path, whereby said actuator coil is energized at periodic intervals.

2 Anelectrical'. cycling timer comprised oar PN unijunction.transistorhaving a iirst'base connector, an emitter anda second base connector, a'fbattery, a first circuit l connecting said battery' through a control switch to said second base connector, said first base connector having a ground connection, a second' circuit connecting said control switch through. a timingv resistor and an' actuator coil tosaid' emitter, capacitancev means connectedto said iirst baseA connector and to said second circuit at a point between said actuatorV coil and said timing resistor, said transistor being triggered when'v said capacitance means is chargedto a predetermined value so that `said actuator coil is energized, means operableby said actuator coil when energized to provide after a predetermined fixed'time. delay a temporary discharge patlrv for said capacitance means and then to open said discharge path so that said actuator coil is energized at periodic intervals, said lastmentioned means including a solenoid and a relayroperable by said actuator coil, said relay being connected to energize said solenoid, said solenoid having contacts which are part of said discharge path and which close after said fixed delay.

3. An electrical cyclingY timer comprised of. av PN unijunction transistor having a first base connector, an emitter and a second oase connector, a battery,. a iirst circuit connecting said battery through a control switch and a temperature compensating resistor to said second base connector, said tirst base connector having a ground connection, a secondi circuit connecting said control switch through atiming resistor and an actuatorcoillto-said emitter, capacitance means connectedl to said first base connector andto said second circuit at a point between said actuator coil and said timing resistor, said transistor beingtr'i'ggeredwhen said capacitance means is charged to a predetermined value so that said actuator coil is energized, a relay having said actuator coil, a solenoid, said relay being connected to energize said solenoid, said solenoid havingv contacts which close afterfa. fixed time delay and connections which provide a discharge path for said capacitance means when said contacts are closed by said solenoid.

4. An electrical cycling timer comprised of a PN unijunction transistor having a-irst base connector, an emitter and a second base connector, a battery having. a positive terminal and a negative terminal, a first circuit connecting said positive terminal of said battery through a control switch to said second base connector, said irst base having a ground connection to the negative'. terminal of said battery, a second circuit connecting. saidv conv trol switch throughv av timing resistor. and a relay. c'oil to said emitter of said transistor, said relay coil being part of a relay havingk normally-open switch means,said normally-open switch means connected to said control switch, a stepper switch having an operatingl coil, said relay switchmeans being connected to said operating coil of said stepper switch, said stepper switch coil having a connection to saidV negative terminalof said battery, capacitance means-connectedto said ground connection of said transistor second base connector and connected to said Y second circuit between said timing resistor' and saidrelay coil, said? capacitance means being such that when charged to a predetermined value it -will trigger said transistor andlsaid relay coil will be energized, said stepper switch coil havingl a return connection to said ground connectionof saidk first base transistor connector so that: it will be energized when said relay is actuated, saidstepper switch requiring a predetermined fixed time for operation and having means arranged so thatI said capacitance means is provided with a discharge path-said` timing. resistor and said capacitance meansv being.A suchthatY said transistor, said relay and saidstepper: switch are operated after predetermined time delays.

5L An electrical cycling timer-comprised'of a PN unijunction transistor having a first base connector, an' emitter and a second'base connector, a battery having a posi- Y tive terminal and a negative terminal?, a rst circuit connecting said positive terminal of'said'battery througha control switch anda temperature compensa-ting resistor to said second base connector, saidiirstbasehaving a ground connection to the negative terminal of` said'battery, a second circuit connecting said control switch through a timing resistor and a relay coil to said emitter of said transistor, said relay coil being partof a. relay having normally-open switch means, said normally-open switch means having first contact means andV movable means contacting second contact means, said` relay coil when energizedbeing constructed to cause contact between said first relay contact means-and said relaymovable means, said iirst relay contact means being connected to said control switch, a stepper switch havingan operating coil, said relay movable means being connected to said operating coil of said stepper switch, said stepper switch coil having a connection to said negative terminal of said battery, capacitance means connected to said ground connection of said transistory second base connector and -connected to said second circuit between said timing resistor and said relay coil, said capacitance means being such that when charged to a predetermined value it will trigger said transistor and said relay coil will be ener gized, said stepper switch coil requiring a predetermined fixed time for operation and having a return connection to said ground connection of said rst base transistor connector so that it will be energized when said relay is actuated, said stepper switch having a contact and movable element arranged to be closed when said stepper switch coil is energized, said stepper switch contact being connected to said return connection of said stepper switch coil, said stepper switch movable element being connected to said second circuit between said timing resistor and said relay coil so that when said stepper switch is closed upon the closing of said relay said capacitance means is provided with a discharge path, said timing resistor and said capacitancemeans being such that said transistor, said relay and said stepper switch are operated after predetermined time delays.

6. An electrical cycling timer comprised of a PN unijunction transistor having a rst base connector, an emitter and a second base connector, a battery having a positive terminal and a negative terminal, a first circuit connecting said positive terminal of said battery through a control switch and a temperature compensating resistor to said second base connector, said first base having a ground connection to the negative terminal of said battery, a second circuit connecting said control switch through a timing resistor and a relay coil to said emitter of said transistor, said relay coil being part of a relay having normallyopen switch means, said normally-open switch means having first contact means and movablemeans contacting second contact means, said relay coil when energized being constructed to cause contact between said first contact means and said movable means, said rst contact means being connected to said control switch, a stepper switch having an operating coil, said movable means being con- .ected to said operating coil of said stepper switch, said stepper switch coil having a connection to said negative terminal of said battery, capacitance means connected to said ground connection or" said transistor second base connector and connected to said second circuit between said timing resistor and said relay coil, said capacitance means being such that when charged to a predetermined value it Will trigger said transistor and said relay coil will be energized, said stepper switch coil having a return connection to said ground connection of said rst base transistor connector so that it will be energized when said relay is actuated, said stepper switch hav-ing a contact and movable element arranged to be closed when said stepper switch coil is energized, said stepper switch contact being connected to said return connection of said .stepper switch coil, said stepper switch movable element being connected to said second circuit between said timing resistor and said relay coil so that when said stepper switch is closed upon the closing of said relay said capacitance means is provided with a discharge path, said timing resistor and said capacitance means being such that said transistor, said relay and said stepper switch are operated after predetermined time delays, arc suppression means including a capacitor connected across said relay movable means and said first relay contact means for offsetting the inductive efect of said stepper switch coil, said second contact means being connected through a resistor to said return connection of said stepper switch coil, said second contact means being connected through a resistor to said return connection of said stepper switch coil to provide a discharge path for said arc suppression capacitor.

References Cited bythe Examiner UNITED STATES PATENTS 2,927,259 3/60 Neal 317-1485 2,964,625 12/60 Brockett 317--142 FOREIGN PATENTS 815,361 6/59 GreatBritain.

LLOYD MCCOLLUM, Primary Examiner. 

6. AN ELECTRICAL CYCLING TIMER COMPRISED OF A PN UNIJUNCTION TRANSISTOR HAVING A FIRST BASE CONNECTOR, AN EMITTER AND A SECOND BASE CONNECTOR, A BATTERY HAVING A POSITIVE TERMINAL AND A NEGATIVE TERMINAL, A FIRST CIRCUIT CONNECTING SAID POSITIVE TERMINAL OF SAID BATTERY THROUGH A CONTROL SWITCH AND A TEMPERATURE COMPENSATING RESISTOR TO SAID SECOND BASE CONNECTOR, SAID FIRST BASE HAVING A GROUND CONNECTION TO THE NEGATIVE TERMINAL OF SAID BATTERY, A SECOND CIRCUIT CONNECTING SAID CONTROL SWITCH THROUGH A TIMING RESISTOR AND A RELAY COIL TO SAID EMITTER OF SAID TRANSISTOR, SAID RELAY COIL BEING PART OF A RELAY HAVING NORMALLYOPEN SWITCH MEANS, SAID NORMALLY-OPEN SWITCH MEANS HAVING FIRST CONTACT MEANS AND MOVABLE MEANS CONTACTING SECOND CONTACT MEANS, SAID RELAY COIL WHEN ENERGIZED BEING CONSTRUCTED TO CAUSE CONTACT BETWEEN SAID FIRST CONTACT MEANS AND SAID MOVABLE MEANS, SAID FIRST CONTACT MEANS BEING CONNECTED TO SAID CONTROL SWITCH, A STEPPER SWITCH HAVING AN OPERATING COIL, SAID MOVABLE MEANS BEING CONNECTED TO SAID OPERATING COIL OF SAID STEPPER SWITCH, SAID STEPPER SWITCH COIL HAVING A CONNECTION TO SAID NEGATIVE TERMINAL OF SAID BATTERY, CAPACITANCE MEANS CONNECTED TO SAID GROUND CONNECTION OF SAID TRANSISTOR SECOND BASE CONNECTOR AND CONNECTED TO SAID SECOND CIRCUIT BETWEEN SAID TIMING RESISTOR AND SAID RELAY COIL, SAID CAPACITANCE MEANS BEING SUCH THAT WHEN CHARGED TO A PREDETERMINED VALUE IT WILL TRIGGER SAID TRANSISTOR AND SAID RELAY COIL WILL BE ENERGIZED, SAID STEPPER SWITCH COIL HAVING A RETURN CONNECTION TO SAID GROUND CONNECTION OF SAID FIRST BASE TRANSISTOR CONNECTOR SO THAT IT WILL BE ENERGIZED WHEN SAID RELAY IS ACTUATED, SAID STEPPER SWITCH HAVING A CONTACT AND MOVABLE ELEMENT ARRANGED TO BE CLOSED WHEN SAID STEPPER SWITCH COIL IS ENERGIZED, SAID STEPPER SWITCH CONTACT BEING CONNECTED TO SAID RETURN CONNECTION OF SAID STEPPER SWITCH COIL, SAID STEPPER SWITCH MOVABLE ELEMENT BEING CONNECTED TO SAID SECOND CIRCUIT BETWEEN SAID TIMING RESISTOR AND SAID RELAY COIL TO THAT WHEN SAID STEPPER SWITCH IS CLOSED UPON THE CLOSING OF SAID RELAY SAID CAPACITANCE MEANS IS PROVIDED WITH A DISCHARGE PATH, SAID TIMING RESISTOR AND SAID CAPACITANCE MEANS BEING SUCH THAT SAID TRANSISTOR, SAID RELAY AND SAID STEPPER SWITCH ARE OPERATED AFTER PREDETERMINED TIME DELAYS, ARC SUPPRESSION MEANS INCLUDING A CAPACITOR CONNECTED ACROSS SAID RELAY MOVABLE MEANS AND SAID FIRST RELAY CONTACT MEANS FOR OFFSETTING THE INDUCTIVE EFFECT OF SAID STEPPER SWITCH COIL, SAID SECOND CONTACT MEANS BEING CONNECTED THROUGH A RESISTOR TO SAID RETURN CONNECTION OF SAID STEPPER SWITCH COIL, SAID SECOND CONTACT MEANS BEING CONNECTED THROUGH A RESISTOR TO SAID RETURN CONNECTION OF SAID STEPPER SWITCH COIL TO PROVIDE A DISCHARGE PATH FOR SAID ARC SUPPRESSION CAPACITOR. 